Traveling hydraulic working machine

ABSTRACT

A traveling hydraulic working machine has input means for commanding a target revolution speed of an engine and detection means for detecting an operating situation of a hydraulic actuator and an operating situation of traveling means. A prime-mover revolution speed control means modifies the target revolution speed of the prime mover when the operating situation of the hydraulic actuator and the operating situation of the traveling means come into respective particular states, and controls the revolution speed of the prime mover. With the traveling hydraulic working machine, in the combined operation of traveling and working a hydraulic actuator, work can be performed on the basis of the engine revolution speed intended by an operator. When a working load varies, the engine revolution speed is automatically controlled.

TECHNICAL FIELD

The present invention relates to a traveling hydraulic working machine,such as a telescopic handler, in which a traveling means, including atorque converter, and a hydraulic pump are coupled to a prime mover(engine) and a working actuator is operated by a hydraulic fluidsupplied from the hydraulic pump while operating the traveling means, tothereby perform predetermined work.

BACKGROUND ART

The related art of that type of traveling hydraulic working machine isdisclosed in JP,B 8-30427 and JP,B 8-30429.

In the related art disclosed in JP,B 8-30427, the engine revolutionspeed is full-automatically controlled through the steps of detectingthe engine revolution speed, the output revolution speed of a torqueconverter, and the delivery pressure of a hydraulic pump, computing thestatus of a machine body based on the detected information, and thencomputing a final throttle command. A target traction force is therebyobtained so that a crawler slippage will not occur.

In the related art disclosed in JP,B 8-30429, a plurality of engineoutput modes are set beforehand, and one of the modes is selected by anoperator depending on a load situation during work, to thereby obtain anengine output required in bulldozing work.

JP,B 8-30427

JP,B 8-30429

DISCLOSURE OF THE INVENTION

When a traveling hydraulic working machine, such as a telescopichandler, is operated to perform work with the combined operation oftraveling and a working actuator, the load pressure of the workingactuator (i.e., the working load) is greatly varied depending on thework situation. In some cases, therefore, the combination of thetraveling and the working actuator becomes improper and the workingefficiency is reduced.

For example, work for excavating natural ground is known as one kind ofwork that is performed with a bucket used as a front attachment. In theexcavation work, the bucket as the front attachment is pushed to thrustinto earth and sand (excavation target) by a travel force while theengine revolution speed is controlled by operating an accelerator pedal.Then, the earth and sand are excavated by applying a front force actingupward to the bucket in such a manner as to gradually displace thebucket upward. When the bucket is pushed to thrust into the earth andsand, heavy load work is performed in which the load pressure of theworking actuator (i.e., the working load) rises and so does the deliverypressure of a hydraulic pump. After the bucket is moved upwardsubsequent to the thrusting of the bucket, the load pressure of theworking actuator (i.e., the working load) lowers and light load work isperformed. In a known general traveling hydraulic working machine,therefore, when the working load is changed from a heavy load to a lightload as mentioned above, the engine revolution speed is increased, thusleading to a problem that the input torque of the torque converter isincreased with the increase of the engine revolution speed, and thebucket overruns when it is moved upward.

As another kind of work, there is surface soil peeling-off work forpeeling off earth and sand at the ground surface by a bucket to form aflat ground surface while the machine is traveled by operating anaccelerator pedal. During such work, the load pressure of the workactuator (i.e., the working load) varies depending on the thickness andhardness of the earth and sand to be peeled off by the bucket. In theknown general traveling hydraulic working machine, therefore, when thebucket strikes against a thick or hard portion of the earth and sand andthe pump delivery pressure (i.e., the working load) rises during thesurface soil peeling-off work, the engine revolution speed is justslightly increased and the traveling speed is hardly reduced.Consequently, the bucket cannot evenly peel off the thick or hardportion of the earth and sand, and a satisfactory flat excavationsurface cannot be formed.

According to the related art disclosed in JP,B 8-30427 (Patent Reference1), the delivery pressure of the hydraulic pump is detected as one itemof the information for judging the status of the machine body. However,the detected pump delivery pressure is used to obtain the final throttlecommand by adding a modification value that corresponds to a pumpabsorption torque. In other words, the detected pump delivery pressureis not used to determine if the working load has changed to a particularstate, and this related art cannot overcome the above-mentioned problemthat is caused when the working load varies and comes into theparticular state. Further, because the engine revolution speed isautomatically controlled regardless of the revolution speed commandedfrom the accelerator pedal, an operator cannot perform work as perintended in the earth-and-sand excavating work and the surface soilpeeling-off work.

In the related art disclosed in JP,B 8-30429 (Patent Reference 2), theworking load is not detected and the engine control is performed only inone of the preset engine output modes. Therefore, this related art alsocannot overcome the above-mentioned problem that is caused when theworking load varies and comes into the particular state.

It is an object of the present invention to provide a travelinghydraulic working machine which can perform work on the basis of theengine revolution speed during the combined operation of traveling and aworking actuator, and which can automatically control the enginerevolution speed in response to a variation of the working load so thatsatisfactory combination can be kept in the combined operation of thetraveling and the working actuator and efficient work can be realized.

(1) To achieve the above object, the present invention provides atraveling hydraulic working machine comprising at least one prime mover,a machine body for mounting the prime mover thereon, traveling meansmounted on the machine body and including a torque converter coupled tothe prime mover, a hydraulic pump driven by the prime mover, at leastone working actuator operated by a hydraulic fluid supplied from thehydraulic pump, and an operating device for generating an operationsignal to control the working actuator, wherein the traveling hydraulicworking machine further comprises input means for commanding a targetrevolution speed of the prime mover; first detection means for detectingan operating situation of the working actuator; second detection meansfor detecting an operating situation of the traveling means; andprime-mover revolution speed control means for modifying the targetrevolution speed of the prime mover based on the operating situation ofthe working actuator detected by the first detection means and theoperating situation of the traveling means detected by the seconddetection means, and controlling the revolution speed of the primemover.

Thus, since the revolution speed of the prime mover is controlled bymodifying the target revolution speed commanded from the input means,work can be performed on the basis of the engine revolution speedintended by the operator.

Also, the revolution speed of the prime mover is controlled by modifyingthe target revolution speed of the prime mover based on the operatingsituation of the working actuator and the operating situation of thetraveling means. Accordingly, even when the working load varies in thecombined operation of traveling and the working actuator, the enginerevolution speed of the prime mover is automatically controlled so thatsatisfactory combination can be kept in the combined operation of thetraveling and the working actuator and efficient work can be realized.

(2) In above (1), preferably, the first detection means includes meansfor detecting at least one of a delivery pressure of the hydraulic pumpand a driving pressure of the working actuator.

With that feature, it is possible to detect the operating situation ofthe working actuator and to control the revolution speed when theworking load varies.

(3) In above (2), preferably, the first detection means further includesmeans for detecting the operation signal generated from the operatingdevice.

With that feature, the operating situation of the working actuator canbe detected including the operating direction of the actuator, and therevolution speed control can be performed in a more appropriate manner.

(4) In above (1), preferably, the second detection means is means fordetecting input and output revolution speeds of the torque converter,and the prime-mover revolution speed control means includes means forcomputing a torque converter speed ratio from input and outputrevolution speeds of the torque converter, and determining the operatingsituation of the traveling means.

With that feature, the operating situation of the traveling means can bedetermined based on the torque converter speed ratio, and the revolutionspeed control of the prime mover can be performed in an appropriatemanner.

(5) In above (1), preferably, the prime-mover revolution speed controlmeans includes means for computing a modification revolution speed ofthe prime mover when the operating situation of the working actuatordetected by the first detection means and the operating situation of thetraveling means detected by the second detection means come intorespective particular states, and means for subtracting the modificationrevolution speed from the target revolution speed of the prime mover.

With that feature, the engine revolution speed is automaticallycontrolled to reduce in response to a variation of the working load.Accordingly, in work requiring the engine revolution speed to be reducedwhen the working load varies, such as work for excavating natural groundand work for peeling off surface soil, satisfactory combination can bekept in the combined operation of the traveling and the working actuatorand efficient work can be realized.

(6) In above (1), preferably, the prime-mover revolution speed controlmeans includes means for modifying the target revolution speed of theprime mover to reduce when the operating situation of the travelingmeans is in a state close to a stall of the torque converter and theoperating situation of the working actuator comes into a light loadstate.

With that feature, in work requiring the engine revolution speed to bereduced when the operating situation of the traveling means is in thestate close to a stall of the torque converter and the working load isreduced, such as the natural ground excavating work, satisfactorycombination can be kept in the combined operation of the traveling andthe working actuator and efficient work can be realized.

(7) In above (1), preferably, the prime-mover revolution speed controlmeans includes means for modifying the target revolution speed of theprime mover to reduce when the operating situation of the travelingmeans is in a state far from a stall of the torque converter and theoperating situation of the working actuator comes into a heavy loadstate.

With that feature, in work requiring the engine revolution speed to bereduced when the operating situation of the traveling means is in thestate far from a stall of the torque converter and the working load isincreased, such as the surface soil peeling-off work, satisfactorycombination can be kept in the combined operation of the traveling andthe working actuator and efficient work can be realized.

(8) In above (1), preferably, the traveling hydraulic working machinefurther comprises third detection means for detecting an input amountfrom the input means, wherein the prime-mover revolution speed controlmeans includes means for modifying the target revolution speed of theprime mover when the input amount detected by the third detection meansis not smaller than a preset value.

With that feature, the prime-mover revolution speed control means is notactivated when the engine revolution speed is in a low-speed range.Therefore, the revolution speed control of the prime mover can beperformed in an appropriate manner only when required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing an overall system of a travelinghydraulic working machine according to a first embodiment of the presentinvention.

FIG. 2 is a side view showing an external appearance of a telescopichandler, the view showing the case where a fork for use in loading andunloading work is mounted as an attachment.

FIG. 3 is a side view showing an external appearance of a telescopichandler, the view showing the case where a bucket for use in excavationwork and surface soil peeling-off work is mounted as an attachment.

FIG. 4 is a functional block diagram showing the processing function ofa controller in the first embodiment of the present invention.

FIG. 5 illustrates excavation work performed by the telescopic handler.

FIG. 6 is a chart showing changes in pump pressure during the excavationwork.

FIG. 7 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in a knowngeneral traveling hydraulic working machine, the graph also showing theoperation state of a traveling system in excavation work.

FIG. 8 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in the firstembodiment of the present invention, the graph also showing theoperation state of a traveling system in excavation work.

FIG. 9 is a circuit diagram showing an overall system of a travelinghydraulic working machine according to a second embodiment of thepresent invention.

FIG. 10 is a functional block diagram showing the processing function ofa controller in the second embodiment of the present invention.

FIG. 11 illustrates the surface soil peeling-off work performed by thetelescopic handler.

FIG. 12 is a chart showing changes in pump pressure during the surfacesoil peeling-off work.

FIG. 13 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in the knowngeneral traveling hydraulic working machine, the graph also showing theoperation state of the traveling system in the surface soil peeling-offwork.

FIG. 14 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in the secondembodiment of the present invention, the graph also showing theoperation state of the traveling system in the surface soil peeling-offwork.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below.

FIG. 1 is a circuit diagram showing an overall system of a travelinghydraulic working machine according to a first embodiment of the presentinvention.

In FIG. 1, a traveling hydraulic working machine according to thisembodiment comprises a diesel engine (hereinafter referred to simply asan “engine”) 1 serving as a prime mover, a working system 2 and atraveling system 3 both driven by the engine 1, and a control system 4for the engine 1.

The working system 2 comprises a hydraulic pump 12 driven by the engine1, a plurality of hydraulic actuators (working actuators) 13, 14, 15 and16 operated by a hydraulic fluid delivered from the hydraulic pump 12,directional control valves 17, 18, 19 and 20 disposed respectivelybetween the hydraulic pump 12 and the plurality of hydraulic actuators(working actuators) 13, 14, 15 and 16, to thereby control flows of thehydraulic fluid supplied to the corresponding actuators, a plurality ofcontrol lever units 23, 24, 25 and 26 for shifting the directionalcontrol valves 17, 18, 19 and 20 and generating pilot pressures(operation signals), and a pilot hydraulic pump 27 for supplying thehydraulic fluid, which serves as an original pressure, to the controllever units 23, 24, 25 and 26.

The traveling system 3 comprises a torque converter 31 coupled to anoutput shaft of the engine 1 in series with respect to the hydraulicpump 12, a transmission (T/M) 32 coupled to an output shaft of thetorque converter 31, and front wheels 35 and rear wheels 36 coupled tothe transmission 32 respectively through differential gears 33, 34.

The engine control system 4 comprises an electronic governor 41 foradjusting a fuel injection amount in the engine 1, an accelerator pedal42 operated by an operator and commanding a target engine revolutionspeed (hereinafter referred to simply as an “target revolution speed”),a position sensor 43 for detecting a tread amount by which theaccelerator pedal 42 is operated (i.e., an accelerator tread amount), apressure sensor 44 for detecting, as an operating situation of thehydraulic actuator, the delivery pressure of the hydraulic pump 2, arotation sensor 45 for detecting an output revolution speed of theengine 1 (i.e., an input revolution speed of the torque converter 31), arotation sensor 46 for detecting an output revolution speed of thetorque converter 31, a pressure sensor 47 for detecting, as an operatingsituation of the hydraulic actuator, a pilot pressure in the extendingdirection of the hydraulic actuator 13 (i.e., a boom-raising pilotpressure) which is one of pilot pressures outputted from the controllever unit 23, and a controller 48 for executing predeterminedarithmetic operations based on input signals from the position sensor43, the pressure sensor 44, the rotation sensors 45, 46 and the pressuresensor 47, and outputting a command signal to the electronic governor41.

FIGS. 2 and 3 each show an external appearance of a telescopic handler(also called a lift truck).

In this embodiment, the traveling hydraulic working machine is, by wayof example, a telescopic handler. The telescopic handler comprises amachine body 101, a cab 102 located on the machine body 101, anextendable boom 103 mounted to the machine body 101 in a manner capableof pivotally rising and lowering laterally of the cab 102, and anattachment 104 or 105 rotatably mounted to a fore end of the boom 103.The front wheels 35 and the rear wheels 36 are mounted to the machinebody 101, and the telescopic handler travels with the front wheels 35and the rear wheels 36 driven by motive power of the engine 1. The boom103 and the attachment 104 or 105 constitute a working device. Theattachment 104 shown in FIG. 2 is a fork for use in loading andunloading work, and the attachment 105 shown in FIG. 3 is a bucket foruse in, e.g., excavation work and surface soil peeling-off work.

Returning to FIG. 1, the hydraulic actuators 13, 14 and 15 are, by wayof example, a boom cylinder, a telescopic cylinder, and an attachmentcylinder, respectively. The boom 103 is pivotally raised or lowered withextension or contraction of the boom cylinder 13, and is extended orcontracted with extension or contraction of the telescopic cylinder 14.The attachment 104 or 105 is tilted with extension or contraction of theattachment cylinder 15. The hydraulic actuator 16 shown in FIG. 1 is ahydraulic motor for rotating a sweeper brush, for example, when asweeper is used as the front attachment. Those components, such as theengine 1, the hydraulic pump 12, the torque converter 31, and thetransmission 32, are mounted to the machine body 101.

FIG. 4 is a functional block diagram showing the processing function ofthe controller 48.

In FIG. 4, the controller 48 has various functions of a reference targetrevolution speed computing unit 51, a first modification revolutionspeed computing unit 52, a speed ratio computing unit 53, a secondmodification revolution speed computing unit 54, a third modificationrevolution speed computing unit 55, a minimum value selector 56, amodification effective/ineffective factor computing unit 57, amultiplier 58, and a subtractor 59.

The reference target revolution speed computing unit 51 receives adetected signal of the accelerator tread amount from the position sensor43 and refers to a table, which is stored in a memory, based on thereceived signal, thereby computing a reference target revolution speedNR corresponding to the accelerator tread amount at that time. Thereference target revolution speed NR represents the engine revolutionspeed intended by the operator during work. In the table stored in thememory, the relationship between the reference target revolution speedNR and the accelerator tread amount is set such that the referencetarget revolution speed NR is increased as the accelerator tread amountincreases.

The first modification revolution speed computing unit 52 receives adetected signal of the pump pressure from the pressure sensor 44 andrefers to a table, which is stored in a memory, based on the receivedsignal, thereby computing a first modification revolution speed ΔN1corresponding to the pump pressure at that time. The first modificationrevolution speed ΔN1 is to reduce the engine revolution speed when thedelivery pressure of the hydraulic pump 12 is low (namely the workingload is small), i.e., when the working system 2 is in a light loadstate. In the table stored in the memory, the relationship between thefirst modification revolution speed ΔN1 and the pump pressure is setsuch that ΔN1=ΔNA holds when the pump pressure is lower than a firstsetting value, ΔN1 is reduced as the pump pressure rises, and ΔN1=0holds when the pump pressure exceeds a second setting value (>firstsetting value).

The speed ratio computing unit 53 receives detected signals of the inputand output revolution speeds of the torque converter 31 from therevolution sensors 45, 46. Then, it executes arithmetic operation ofe=output revolution speed/input revolution speed to compute a torqueconverter speed ratio e.

The second modification revolution speed computing unit 54 receives thetorque converter speed ratio e computed by the speed ratio computingunit 53 and refers to a table, which is stored in a memory, based on thereceived signal, thereby computing a second modification revolutionspeed ΔN2 corresponding to the torque converter speed ratio e at thattime. The second modification revolution speed ΔN2 is to reduce theengine revolution speed when the torque converter speed ratio e is small(namely the torque converter 31 is in a state close to a stall), i.e.,when the traveling system 3 is in an operating situation requiring atraction force (travel force). In the table stored in the memory, therelationship between the second modification revolution speed ΔN2 andthe torque converter speed ratio e is set such that ΔN2=ΔNB holds whenthe torque converter speed ratio e is smaller than a first settingvalue, ΔN2 is reduced as the torque converter speed ratio e increases,and ΔN2=0 holds when the torque converter speed ratio e exceeds a secondsetting value (>first setting value).

The third modification revolution speed computing unit 55 receives adetected signal of the boom-raising pilot pressure from the pressuresensor 47 and refers to a table, which is stored in a memory, based onthe received signal, thereby computing a third modification revolutionspeed ΔN3 corresponding to the boom-raising pilot pressure at that time.The third modification revolution speed ΔN3 is to reduce the enginerevolution speed when the boom raising operation is performed. In thetable stored in the memory, the relationship between the thirdmodification revolution speed ΔN3 and the boom-raising pilot pressure isset such that ΔN3=ΔNC holds when the boom-raising pilot pressure exceedsa setting value close to 0.

The minimum value selector 56 selects a minimum value among the firstmodification revolution speed ΔN1, the second modification revolutionspeed ΔN2, and the third modification revolution speed ΔN3, and sets theselected value as a modification revolution speed ΔN. Herein, by way ofexample, ΔNA in the first modification revolution speed computing unit52, ΔNB in the second modification revolution speed computing unit 54,and ΔNC in the third modification revolution speed computing unit 55 areset to satisfy ΔNA=ΔNB=ΔNC. Then, when the first modification revolutionspeed computing unit 52, the second modification revolution speedcomputing unit 54, and the third modification revolution speed computingunit 55 compute ΔNA, ΔNB and ΔNC, respectively, the minimum valueselector 56 selects minimum one of them, e.g., ΔNA, in accordance withthe preset logic.

The modification effective/ineffective factor computing unit 57 receivesthe detected signal of the accelerator tread amount from the positionsensor 43 and refers to a table, which is stored in a memory, based onthe received signal, thereby computing a modificationeffective/ineffective factor K corresponding to the accelerator treadamount at that time. The modification effective/ineffective factor K isused not to reduce the engine revolution speed when the targetrevolution speed intended by the operator during work is in a low-speedrange and a reduction of the engine revolution speed is not required(namely, the factor K is used to reduce the engine revolution speed onlywhen the target revolution speed is in a medium- or high-speed range).In the table stored in the memory, the relationship between themodification effective/ineffective factor K and the accelerator treadamount is set such that K=0 holds when the accelerator tread amount issmaller than a first setting value, K is increased as the acceleratortread amount increases from the first setting value, and K=1 holds whenthe accelerator tread amount exceeds a second setting value (>firstsetting value). The reason why K is set to increase as the acceleratortread amount increases from the first setting value resides in making itpossible to reduce the engine revolution speed in a corresponding waywhen the target revolution speed is in the medium-speed range. If thatfunction is not required, the above relationship may be set in anON/OFF-like manner such that K=0 holds when the accelerator tread amountis smaller than the second setting value or a nearby value, and K=1holds when the accelerator tread amount exceeds the second setting valueor the nearby value. This setting makes it possible to reduce the enginerevolution speed only when the target revolution speed is in thehigh-speed range.

The multiplier 58 multiplies the modification revolution speed ΔNselected by the minimum value selector 56 by the factor K computed bythe modification effective/ineffective factor computing unit 57 toobtain a final modification revolution speed ΔN.

The subtractor 59 subtracts the modification revolution speed ΔNcomputed by the multiplier 58 from the reference target revolution speedNR computed by the reference target revolution speed computing unit 51to obtain a target revolution speed NT for engine control. The targetrevolution speed NT is converted to a target fuel injection amount in aknown manner, which is outputted as a command signal to the electronicgovernor 41.

In the arrangement described above, the accelerator pedal 42 and theposition sensor 43 constitute input means for commanding the targetrevolution speed of the engine 1 serving as the prime mover. Thepressure sensors 44, 47 constitute first detection means for detectingthe operating situation of the hydraulic actuator 13, etc. serving asthe working actuators. The rotation sensors 45, 46 constitute seconddetection means for detecting the operating situation of travelingmeans. The various functions of the reference target revolution speedcomputing unit 51, the first modification revolution speed computingunit 52, the speed ratio computing unit 53, the second modificationrevolution speed computing unit 54, the third modification revolutionspeed computing unit 55, the minimum value selector 56, and thesubtractor 59 in the controller 48 constitute prime-mover revolutionspeed control means for modifying the target revolution speed of theprime mover 1 based on the operating situation of the hydraulic actuator13, etc. detected by the first detection means 44, 47 and the operatingsituation of the traveling means detected by the second detection means45, 46, and controlling the revolution speed of the prime mover.

The operation of this embodiment will be described below.

FIG. 5 illustrates how work for excavating natural ground is performedby the telescopic handler with the bucket 105 mounted as the attachment.FIG. 6 is a chart showing changes in the delivery pressure of thehydraulic pump 12 (i.e., the pump pressure) during the excavation work.

In the natural ground excavating work, the accelerator pedal 42 (FIG. 1)is operated to set the revolution speed of the engine 1 to a desiredvalue, while the bucket 105 is pushed to thrust into earth and sand 200of the natural ground by a travel force Ft outputted from the engine 1through the torque converter 31. Then, the earth and sand are excavatedby operating the boom cylinder 13 and the attachment cylinder 15(FIG. 1) to raise the boom 103 and tilt the bucket 105, respectively,thereby giving the bucket 105 with an upward front force Ff such thatthe bucket 105 is gradually displaced upward. In that work, when thebucket is 105 pushed to thrust into the earth and sand, the loadpressure of the boom cylinder 13 and/or the attachment cylinder 15serving as the working actuators (i.e., the working load) rises and sodoes the delivery pressure of the hydraulic pump 12 (FIG. 1) (heavy loadwork; zone A in FIG. 6). After the bucket 105 is moved upward subsequentto the thrusting of the bucket 105, the load pressure of the workingactuators 13, 15 (i.e., the working load) lowers and so does the pumppressure (light load work; zone B in FIG. 6).

FIG. 7 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in a knowngeneral traveling hydraulic working machine, the graph also showing theoperation state in the excavation work, shown in FIGS. 5 and 6, oncondition that the target revolution speed (reference target revolutionspeed NR in FIG. 4) commanded from the accelerator pedal is set to amaximum (rated) value NRmax. In FIG. 7, TE represents a characteristicof the engine output torque in a full load region where the fuelinjection amount of the electronic governor 41 is maximized. TRrepresents a characteristic of the engine output torque in a regulationregion before the fuel injection amount of the electronic governor 41 ismaximized. TPA represents the pump absorption torque (maximum pumpabsorption torque) in, e.g., a combined stall state where the hydraulicpump 12 consumes a maximum absorption torque. TEP represents acharacteristic of the torque converter input torque resulting bysubtracting TP from TE, when the hydraulic pump 12 consumes the maximumabsorption torque. TT represents a characteristic of the torqueconverter input torque in a full load region when the torque converter31 is in a stall state. The stall state of the torque converter 31 meansthe state where the output revolution speed is 0, i.e., the state of thespeed ratio e=0. Also, the term “combined stall state” means the statewhere the torque converter 31 is in the stall state (e=0), and thedelivery pressure of the hydraulic pump 12 rises to the setting pressureof a main relief valve (not shown) and is in a relief state.

In the excavation work shown in FIGS. 5 and 6, the operation state inthe zone A, in which the bucket is pushed to thrust into the earth andsand, corresponds to a point A in FIG. 7, and the operation state in thezone B, in which the bucket is moved upward after the thrusting of thebucket, corresponds to a point B in FIG. 7.

In the excavation work shown in FIGS. 5 and 6, the traveling speed ofthe telescopic handler is near 0 and the torque converter 31 issubstantially in the stall state (e=0). Also, in the thrusting operationof the bucket, the pump pressure rises to the relief pressure and thepump absorption torque is maximized to TPA, thus resulting in thecombined stall state (heavy load state) (point A). When the bucket 105is moved upward after the thrusting of the bucket, the pump pressurelowers and the pump absorption torque is reduced from TPA to TPB, thusresulting in a light load state (point B). As a consequence, theoperating point of the traveling system shifts from the point A to B,and the actual engine revolution speed is increased from NA at the pointA to NB at the point B.

Thus, the known general traveling hydraulic working machine has theproblem that when the working load is changed from a heavy load to alight load, the actual engine revolution speed is increased from NA toNB and, with this increase of the engine revolution speed, the inputtorque of the torque converter 31 is increased from TTA to TTB, whichresults in excessive thrusting of the bucket 105.

FIG. 8 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in thisembodiment, the graph also showing the operation state in the excavationwork, shown in FIG. 5, on condition that the target revolution speed(reference target revolution speed NR in FIG. 4) commanded from theaccelerator pedal 42 is set to a maximum (rated) value NRmax.

According to this embodiment, in the excavation work shown in FIGS. 5and 6, the controller 48 executes the processing, described below, forcontrol of the engine revolution speed in the thrusting operation of thebucket.

First, the reference target revolution speed computing unit 51 computes,as the reference target revolution speed, the maximum target revolutionspeed NRmax based on the accelerator tread amount inputted through theaccelerator pedal 42.

In the thrusting operation of the bucket, the pump pressure rises to therelief pressure (heavy load work; zone A in FIG. 6), and the firstmodification revolution speed computing unit 52 computes ΔN1=0.

Also, in the excavation work, the torque converter 31 is in the stateclose to a stall where its output revolution speed is 0, and the speedratio computing unit 53 computes e≈0. Therefore, the second modificationrevolution speed computing unit 54 computes ΔN2=ΔNB.

Further, in the thrusting operation of the bucket, the thirdmodification revolution speed computing unit 55 computes ΔN3=0 when theboom raising operation is not performed, and it computes ΔN3=ΔNC whenthe boom raising operation is performed.

Accordingly, the minimum value selector 56 selects ΔN=0.

On the other hand, since the accelerator pedal 42 is in the operatedstate to command the maximum target revolution speed NRmax, themodification effective/ineffective factor computing unit 57 computesK=1, and the multiplier 58 computes ΔN=0×1=0.

As a result, the subtractor 59 computes NT=NRmax−0=NRmax. In otherwords, the target revolution speed NRmax commanded from the acceleratorpedal 42 is used, as it is, as the target revolution speed for control,and the engine revolution speed is controlled in the same manner as inthe related art. Thus, in FIG. 8, the traveling system 3 operates at thesame point A as in the related art, and the actual engine revolutionspeed is NA.

When the bucket is moved upward after the thrusting of the bucket, thecontroller 48 executes the processing, described below, for the enginerevolution speed control.

First, the reference target revolution speed computing unit 51 computes,as the reference target revolution speed, the maximum target revolutionspeed NRmax as in the thrusting operation of the bucket.

When the bucket is moved upward after the thrusting of the bucket, thepump pressure lowers (light load work; zone B in FIG. 6), and the firstmodification revolution speed computing unit 52 computes ΔN1=ΔNA.

Also, when the bucket is moved upward after the thrusting of the bucket,the torque converter 31 is in the state close to a stall where itsoutput revolution speed is 0. Therefore, the speed ratio computing unit53 computes e≈0, and the second modification revolution speed computingunit 54 computes ΔN2=ΔNB.

Further, when the bucket is moved upward after the thrusting of thebucket, the third modification revolution speed computing unit 55computes ΔN3=ΔNC when the boom cylinder 13 is extended to perform theboom raising operation.

Accordingly, the minimum value selector 56 selects ΔN=MIN(ΔNA, ΔNB,ΔNC), e.g., ΔN=ΔNA.

On the other hand, since the accelerator pedal 42 is in the statedoperated to command the maximum target revolution speed NRmax, themodification effective/ineffective factor computing unit 57 computesK=1, and the multiplier 58 computes ΔN=ΔNA×1=ΔNA.

As a result, the subtractor 59 computes NT=NRmax−ΔNA. In other words,the target revolution speed for control is reduced by ΔNA from therevolution speed set by the accelerator pedal 41, and the engine controlis performed based on that target revolution speed.

In FIG. 8, Nx represents the reduced target revolution speed(NT=NRmax−ΔNA). Thus, in this embodiment, since the target revolutionspeed is reduced when the bucket is moved upward after the thrusting ofthe bucket, the actual engine revolution speed is hardly changed fromthat in the thrusting operation of the bucket in spite of lowering ofthe pump pressure (working load), whereby the engine revolution speed isheld substantially at the same value as that in the thrusting operationof the bucket, i.e., a value near the point A. Consequently, it ispossible to prevent the excessive thrusting of the bucket 105 that hasoccurred in the related art. In addition, the engine revolution speed isreduced and therefore fuel economy is improved.

According to this embodiment, as described above, in the work forexcavating natural ground with the combined operation of the travelingand the working actuator, the work can be performed on the basis of theengine revolution speed intended by the operator. Also, when the workingload reduces, the engine revolution speed is automatically reduced so asto keep satisfactory combination in the combined operation of thetraveling and the working actuator and to realize efficient work. Inaddition, since the engine revolution speed is reduced, fuel economy canbe improved.

Further, according to this embodiment, because of detecting not only thepump pressure, but also the boom-raising pilot pressure as the operatingsituation of the hydraulic actuator 13, the excavation work can bedetected in an accurate way.

Moreover, since the modification effective/ineffective factor computingunit 57 is provided so as not to execute the control for reducing theengine revolution speed when the engine revolution speed is in thelow-speed range, an undesired reduction of the engine revolution speedcan be avoided.

A second embodiment of the present invention will be described withreference to FIGS. 9 through 14. In this embodiment, the surface soilpeeling-off work is performed using the telescopic handler.

FIG. 9 is a circuit diagram showing an overall system of a travelinghydraulic working machine according to this embodiment. In thisembodiment, as means disposed in an engine control system 4A fordetecting the operating situation of the hydraulic actuator, a pressuresensor 47A for detecting a boom-lowering pilot pressure outputted fromthe control lever unit 23 is disposed instead of the pressure sensordisposed in the first embodiment for detecting the boom-raising pilotpressure outputted from the control lever unit 23. A controller 48Aexecutes predetermined arithmetic operations based on input signals fromthe pressure sensor 47A, the position sensor 43, the pressure sensor 44,and the rotation sensors 45, 46, and outputs a command signal to theelectronic governor 41. The other arrangement of the overall system isthe same as that in the first embodiment.

FIG. 10 is a functional block diagram showing the processing function ofthe controller 48A in this embodiment. In FIG. 10, components having thesame functions as those in FIG. 4 are denoted by the same symbols.

In FIG. 10, the controller 48 in this embodiment has various functionsof a reference target revolution speed computing unit 51, a firstmodification revolution speed computing unit 52A, a speed ratiocomputing unit 53, a second modification revolution speed computing unit54A, a third modification revolution speed computing unit 55A, a minimumvalue selector 56, a modification effective/ineffective factor computingunit 57, a multiplier 58, and a subtractor 59.

The first modification revolution speed computing unit 52A receives adetected signal of the pump pressure from the pressure sensor 44 andrefers to a table, which is stored in a memory, based on the receivedsignal, thereby computing a first modification revolution speed ΔN1corresponding to the pump pressure at that time. The first modificationrevolution speed ΔN1 is to reduce the engine revolution speed when thedelivery pressure of the hydraulic pump 12 is high (namely the workingload is large), i.e., when the working system 2 is in a heavy loadstate. In the table stored in the memory, the relationship between thefirst modification revolution speed ΔN1 and the pump pressure is setsuch that ΔN1=0 holds when the pump pressure is lower than a firstsetting value, ΔN1 is increased as the pump pressure rises, and ΔN1=ΔNAholds when the pump pressure exceeds a second setting value (>firstsetting value).

The second modification revolution speed computing unit 54A receives atorque converter speed ratio e computed by the speed ratio computingunit 53 and refers to a table, which is stored in a memory, based on thereceived signal, thereby computing a second modification revolutionspeed ΔN2 corresponding to the torque converter speed ratio e at thattime. The second modification revolution speed ΔN2 is to reduce theengine revolution speed when the torque converter speed ratio e is large(namely the torque converter 31 is in a state far from a stall), i.e.,when the traveling system 3 is in an operating situation not requiring atraction force (travel force). In the table stored in the memory, therelationship between the second modification revolution speed ΔN2 andthe torque converter speed ratio e is set such that ΔN2=0 holds when thetorque converter speed ratio e is smaller than a first setting value,ΔN2 is increased as the torque converter speed ratio e increases, andΔN2=ΔNB holds when the torque converter speed ratio e exceeds a secondsetting value (>first setting value).

The third modification revolution speed computing unit 55 receives adetected signal of the boom-lowering pilot pressure from the pressuresensor 47A, and refers to a table, which is stored in a memory, based onthe received signal, thereby computing a third modification revolutionspeed ΔN3 corresponding to the boom-lowering pilot pressure at thattime. The third modification revolution speed ΔN3 is to reduce theengine revolution speed when the boom lowering operation is performed.In the table stored in the memory, the relationship between the thirdmodification revolution speed ΔN3 and the boom-lowering pilot pressureis set such that ΔN3=ΔNC holds when the boom-lowering pilot pressureexceeds a value close to 0.

The other functions, i.e., the functions of the reference targetrevolution speed computing unit 51, the speed ratio computing unit 53,the minimum value selector 56, the modification effective/ineffectivefactor computing unit 57, the multiplier 58, and the subtractor 59 arethe same as those in the first embodiment. More specifically, theminimum value selector 56 selects a minimum value among the firstmodification revolution speed ΔN1, the second modification revolutionspeed ΔN2, and the third modification revolution speed ΔN3, and sets theselected value as a modification revolution speed ΔN. The multiplier 58multiplies the modification revolution speed ΔN selected by the minimumvalue selector 56 by a factor K computed by the modificationeffective/ineffective factor computing unit 57 to obtain a finalmodification revolution speed ΔN. The subtractor 59 subtracts themodification revolution speed ΔN computed by the multiplier 58 from thereference target revolution speed NR computed by the reference targetrevolution speed computing unit 51 to obtain a target revolution speedNT for engine control. The target revolution speed NT is converted to atarget fuel injection amount in a known manner, which is outputted as acommand signal to the electronic governor 41.

The operation of this embodiment will be described below.

FIG. 11 illustrates how the surface soil peeling-off work is performedby the telescopic handler with the bucket 105 mounted as the attachment.Also in the surface soil peeling-off work, the bucket 105 is mounted asthe attachment. FIG. 12 is a chart showing changes in the deliverypressure of the hydraulic pump 12 (i.e., the pump pressure) during thesurface soil peeling-off work.

In the surface soil peeling-off work, the accelerator pedal 42 (FIG. 1)is operated for traveling at a desired engine revolution speed, whilethe boom cylinder 13 and the attachment cylinder 15 (FIG. 1) areoperated to lower the boom and tilt the bucket, respectively, therebyapplying a downward front force Ff to the bucket 105 to be pressedagainst the ground such that the bucket 105 peels off rugged earth andsand 201 at the ground surface to form a flat ground surface. In thatwork, the load pressure of the boom cylinder 13 and the attachmentcylinder 15 (i.e., the working load) is changed depending on thethickness and hardness of the surface earth and sand 201 to be peeledoff by the bucket. More specifically, when the earth and sand have athin thickness or are soft, the load pressure of the boom cylinder 13and/or the attachment cylinder 15 (i.e., the working load) lowers (heavyload work; zone E in FIG. 12). When the bucket 105 strikes against athick or hard portion of the earth and sand, the load pressure of theboom cylinder 13 and/or the attachment cylinder 15 (i.e., the workingload) rises (light load work; zone F in FIG. 12).

FIG. 13 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in the knowngeneral traveling hydraulic working machine, the graph also showing theoperation state in the surface soil peeling-off work, shown in FIGS. 11and 12, on condition that the target revolution speed (reference targetrevolution speed NR in FIG. 10) commanded from the accelerator pedal isset to a maximum (rated) value NRmax. In FIG. 13, TE, TR and TEPrepresent the same characteristics as those described above inconnection with FIG. 7. TTE represents a characteristic of the torqueconverter input torque when the torque converter 31 is in a travel state(i.e., a state far from a stall (e=0). The characteristic at e=0.8 isshown as one example.

In the surface soil peeling-off work shown in FIGS. 11 and 12, theoperation state in the zone E, in which the earth and sand have a thinthickness or are soft, corresponds to a point E in FIG. 13, and theoperation state in the zone F, in which the bucket 105 strikes against athick or hard portion of the earth and sand, corresponds to a point F inFIG. 12.

In the surface soil peeling-off work shown in FIGS. 11 and 12, becausethe telescopic handler performs work while traveling, the outputrevolution speed of the torque converter 31 is relatively higher and thespeed ratio is, for example, near e=0.8. Also, when the earth and sandto be peeled off have a thin thickness or are soft, the pump pressure islow and the pump absorption torque is small at a level of, e.g., aboutTPE as shown (point E). When the bucket 105 strikes against a thick orhard portion of the earth and sand, the pump pressure rises and the pumpabsorption torque is increased from TPE to TPF (point F). As aconsequence, the operating point of the traveling system shifts from thepoint E to F, and the actual engine revolution speed is slightly reducedfrom NE at the point E to EF at the point F.

Thus, in the known general traveling hydraulic working machine, when thebucket strikes against a thick or hard portion of the earth and sandduring the surface soil peeling-off work and the pump pressure (workingload) rises, the actual engine revolution speed is just slightly reducedfrom NE to EF, and the traveling speed is hardly reduced. Therefore, thebucket 105 is moved at a high speed in spite of the earth and sand beingthick or hard, and peels off the earth and sand in a forcible way,whereby a satisfactory flat excavation surface cannot be formed.

FIG. 14 is a graph showing the relationship among engine output torque,pump absorption torque, and torque converter input torque in thisembodiment, the graph also showing the operation state in the surfacesoil peeling-off work, shown in FIGS. 11 and 12, on condition that thetarget revolution speed (reference target revolution speed NR in FIG.10) commanded from the accelerator pedal 42 is set to a maximum (rated)value NRmax.

According to this embodiment, in the surface soil peeling-off work shownin FIGS. 11 and 12, the controller 48A executes the processing,described below, for control of the engine revolution speed when theearth and sand have a thin thickness or are soft.

First, the reference target revolution speed computing unit 51 computes,as the reference target revolution speed, the maximum target revolutionspeed NRmax based on the accelerator tread amount inputted through theaccelerator pedal 42.

When the earth and sand to be peeled off have a thin thickness or aresoft, the pump pressure lowers (light load work; zone E in FIG. 12), andthe first modification revolution speed computing unit 52A computesΔN1=0.

Also, in the surface soil peeling-off work, the output revolution speedof the torque converter 31 is relatively higher (far from the stallstate). Therefore, the speed ratio computing unit 53 computes e=0.8, forexample, as the speed ratio, and the second modification revolutionspeed computing unit 54A computes ΔN2=ΔNB.

Further, because the boom lowering operation is performed in the surfacesoil peeling-off work, the third modification revolution speed computingunit 55A computes ΔN3=ΔNC.

Accordingly, the minimum value selector 56 selects ΔN=0.

On the other hand, since the accelerator pedal 42 is in the operatedstate to command the maximum target revolution speed NRmax, themodification effective/ineffective factor computing unit 57 computesK=1, and the multiplier 58 computes ΔN=0×1=0.

As a result, the subtractor 59 computes NT=NRmax−0=NRmax. In otherwords, the target revolution speed NRmax commanded from the acceleratorpedal 42 is used, as it is, as the target revolution speed for control,and the engine revolution speed is controlled in the same manner as inthe related art. Thus, in FIG. 14, the traveling system 3 operates atthe same point E as in the related art, and the actual engine revolutionspeed is NE.

When the bucket 105 strikes against a thick or hard portion of the earthand sand, the controller 48A executes the processing, described below,for the engine revolution speed control.

First, the reference target revolution speed computing unit 51 computes,as the reference target revolution speed, the maximum target revolutionspeed NRmax as when the earth and sand to be peeled off have a thinthickness or are soft.

When the bucket 105 strikes against a thick or hard portion of the earthand sand, the pump pressure rises (heavy load work; zone F in FIG. 12),and the first modification revolution speed computing unit 52A computesΔN1=ΔNA.

Also, in the surface soil peeling-off work, even when the bucket 105strikes against a thick or hard portion of the earth and sand, thetelescopic handler continues traveling and the torque converter 31 is inthe state far from a stall. Therefore, the speed ratio computing unit 53computes e=0.75 as the speed ratio, and the second modificationrevolution speed computing unit 54A computes ΔN2=ΔNB.

Further, because the boom lowering operation is performed in the surfacesoil peeling-off work, the third modification revolution speed computingunit 55A computes ΔN3=ANC.

Accordingly, the minimum value selector 56 selects ΔN=MIN(ΔNA, ΔNB,ΔNC), e.g., ΔN=ΔNA.

On the other hand, since the accelerator pedal 42 is in the operatedstate to command the maximum target revolution speed NRmax, themodification effective/ineffective factor computing unit 57 computesK=1, and the multiplier 58 computes ΔN=ΔNA×1=ΔNA.

As a result, the subtractor 59 computes NT=NRmax−ΔNA. In other words,the target revolution speed for control is reduced by ΔNA from therevolution speed set by the accelerator pedal 41, and the engine controlis performed based on that target revolution speed.

In FIG. 14, Ny represents the reduced target revolution speed(NT=NRmax−ΔNA), and TTJ represents the torque converter input torque ate=0.75, for example, after the engine revolution speed has been reduced.

In this embodiment, when the bucket 105 strikes against a thick or hardportion of the earth and sand, the pump pressure rises and the pumpabsorption torque is increased from TPE to TPF, which results in theincreased working load. Simultaneously, as described above, the targetrevolution speed is reduced and the operating point of the travelingsystem 3 shifts from the point E to J. TPJ represents the torqueconverter input torque after the shift of the operating point. As aconsequence, the actual engine revolution speed is reduced from NE atthe point E to NF at the point J, and the traveling speed is alsoreduced correspondingly. Hence, the bucket 105 is able to gentlyexcavate the thick or hard portion of the earth and sand while travelingat a slow speed, and to form a satisfactory flat excavation surface.

In FIG. 14, Ny represents the reduced target revolution speed(NT=NRmax−ΔNA), the operating point of the traveling system 3 shiftsfrom the point E to J, and the actual engine revolution speed is reducedfrom NE at the point E to NF at the point J. TTJ represents acharacteristic of the torque converter input torque at e=0.75, forexample, after the engine revolution speed has been reduced, and TPJrepresents the torque converter input torque after the shift of theoperating point.

Thus, in this embodiment, when the bucket 105 strikes against a thick orhard portion of the earth and sand, the pump pressure rises and the pumpabsorption torque is increased from TPE to TPF, which results in theincreased working load. Simultaneously, the target revolution speed isreduced and the operating point of the traveling system 3 shifts fromthe point E to J, whereby the actual engine revolution speed is reducedfrom NE to NF and the traveling speed is also reduced correspondingly.As a result, the bucket 105 is able to gently excavate the thick or hardportion of the earth and sand while traveling at a slow speed, and toform a satisfactory flat excavation surface. In addition, since theengine revolution speed is reduced, fuel economy can be improved.

According to this embodiment, as described above, the followingadvantages can be obtained. In the surface soil peeling-off work withthe combined operation of the traveling and the working actuator, thework can be performed on the basis of the engine revolution speedintended by the operator. Also, when the working load increases, theengine revolution speed is automatically controlled so as to keepsatisfactory combination in the combined operation of the traveling andthe working actuator and to realize efficient work. In addition, sincethe engine revolution speed is reduced, fuel economy can be improved.

While the above embodiments have been described in connection with, asexamples of work, the natural ground excavating work (first embodiment)and the surface soil peeling-off work (second embodiment), the presentinvention is not limited to those kinds of work.

For example, the second embodiment has been described in connection withthe case of performing the surface soil peeling-off work by using thetelescopic handler. However, the present invention is also applicable tothe case of performing cleaning work with a sweeper mounted as theattachment. In the cleaning work using the sweeper, the telescopichandler travels while the sweeper is pressed against a road with theboom lowering operation, and the hydraulic motor 16 shown in FIG. 1 isrotated to rotate a sweeper brush such that droppings, such asrubbishes, on the road are collected into a hopper. In such work, therelated art accompanies the problem that, because the engine revolutionspeed is not so changed even with an increase of substances to beremoved, the traveling speed is not changed and some of the substancesare left over. According to the system of the second embodiment, whenthe substances to be removed are increased in the cleaning work usingthe sweeper, the target revolution speed is automatically reduced and sois the actual engine revolution speed as in the case of the surface soilpeeling-off work. Therefore, the traveling speed is slowed down and thesubstances to be removed are avoided from being left over.

Also, while the embodiments have been described as using the telescopichandler as the traveling hydraulic working machine, similar advantagescan be similarly obtained in applications to other types of travelinghydraulic working machines so long as the machines include torqueconverters. Examples of the traveling hydraulic working machinesequipped with torque converters, other than the telescopic handler, area wheel shovel and a wheel loader.

Further, in the embodiments described above, the first modificationrevolution speed computing unit 52 or 52A receives the detected signalof the pump pressure from the pressure sensor 44, and determines theload state of the working system 2. Alternatively, a pressure sensor fordetecting the driving pressure of the hydraulic actuator 13, etc. may beprovided, and the first modification revolution speed computing unit 52or 52A may receive a detected signal from that pressure sensor.

The first to third modification revolution speed computing units 52, 54,55 or 52A, 54A, 55A each compute the modification revolution speed(value of 0 to 1) as a value for changing the engine revolution speed,and the subtractor 59 subtracts the modification revolution speed fromthe reference target revolution speed. Alternatively, it is alsopossible to provide a unit for computing a modification factor insteadof the modification revolution speed computing unit, to provide amultiplier instead of the subtractor, and to multiply the referencetarget revolution speed by the modification factor, thereby obtainingthe target revolution speed for control.

Moreover, in addition to the pump pressure, the boom-raising orboom-lowering pilot pressure is detected as means for detecting theoperating situation of the working actuator, and the modification valueof the engine revolution speed is determined depending on each of thosepressures. In the case of going to control the engine revolution speedupon change of the working load regardless of the operating direction ofthe actuator, however, only the pump pressure may be detected to computethe modification revolution speed. In that case, the third modificationrevolution speed computing unit 55 or 55A is not required. Also, in thecase of providing, as the means for detecting the operating situation ofthe working actuator, means for detecting operation signals generatedfrom operating devices, two or more operation signals may be detectedinstead of detecting one operation signal (i.e., the boom-raising orboom-lowering pilot pressure). In that case, the operating situation ofthe working actuator can be confirmed with higher accuracy.

Additionally, when the work requiring the engine revolution speed to becontrolled upon change of the working load is restricted to work of thetype that the target revolution speed is always set to a high-speedrange, the modification effective/ineffective factor computing unit 57can be dispensed with.

INDUSTRIAL APPLICABILITY

According to the present invention, when a traveling hydraulic workingmachine is operated to perform work with the combined operation oftraveling and a hydraulic actuator (working actuator), the revolutionspeed of a prime mover is controlled by modifying the target revolutionspeed inputted from input means, and therefore the work can be performedon the basis of the engine revolution speed intended by the operator.Also, even when the load pressure of the working actuator (i.e., theworking load) varies depending on the working situation, the revolutionspeed of the prime mover is automatically controlled so thatsatisfactory combination can be kept in the combined operation of thetraveling and the working actuator and efficient work can be realized.

1. A traveling hydraulic working machine comprising at least one primemover (1), a machine body (101) for mounting said prime mover thereon,traveling means (3) mounted on said machine body and including a torqueconverter (31) coupled to said prime mover, a hydraulic pump (12) drivenby said prime mover, at least one working actuator (13-16) operated by ahydraulic fluid supplied from said hydraulic pump, and an operatingdevice (23-26) for generating an operation signal to control saidworking actuator, said traveling hydraulic working machine furthercomprising: input means (42) for commanding a target revolution speed ofsaid prime mover (1); first detection means (47) for detecting anoperating situation of said working actuator (13-16); second detectionmeans (45, 46) for detecting an operating situation of said travelingmeans (3); and prime-mover revolution speed control means (52-59) formodifying the target revolution speed of said prime mover based on theoperating situation of said working actuator detected by said firstdetection means and the operating situation of said traveling meansdetected by said second detection means, and controlling the revolutionspeed of said prime mover.
 2. The traveling hydraulic working machineaccording to claim 1, wherein said first detection means includes means(44) for detecting at least one of a delivery pressure of said hydraulicpump (12) and a driving pressure of said working actuator (13-16). 3.The traveling hydraulic working machine according to claim 2, whereinsaid first detection means further includes means (47A) for detectingthe operation signal generated from said operating device (23).
 4. Thetraveling hydraulic working machine according to claim 1, wherein saidsecond detection means is means (45, 46) for detecting input and outputrevolution speeds of said torque converter (31), and said prime-moverrevolution speed control means includes means (53, 54) for computing atorque converter speed ratio from input and output revolution speeds ofsaid torque converter, and determining the operating situation of saidtraveling means (3).
 5. The traveling hydraulic working machineaccording to claim 1, wherein said prime-mover revolution speed controlmeans includes means (52-56) for computing a modification revolutionspeed of said prime mover (1) when the operating situation of saidworking actuator (13-16) detected by said first detection means (44) andthe operating situation of said traveling means (3) detected by saidsecond detection means (45, 46) come into respective particular states,and means (59) for subtracting the modification revolution speed fromthe target revolution speed of said prime mover.
 6. The travelinghydraulic working machine according to claim 1, wherein said prime-moverrevolution speed control means includes means (52-54, 56, 59) formodifying the target revolution speed of said prime mover (1) to reducewhen the operating situation of said traveling means (3) is in a stateclose to a stall of said torque converter and the operating situation ofsaid working actuator (13-16) comes into a light load state.
 7. Thetraveling hydraulic working machine according to claim 1, wherein saidprime-mover revolution speed control means includes means (52A, 53, 54A,56, 59) for modifying the target revolution speed of said prime mover(1) to reduce when the operating situation of said traveling means (3)is in a state far from a stall of said torque converter and theoperating situation of said working actuator (13-16) comes into a heavyload state.
 8. The traveling hydraulic working machine according toclaim 1, further comprising third detection means (43) for detecting aninput amount from said input means (42), wherein said prime-moverrevolution speed control means includes means (57, 58) for modifying thetarget revolution speed of said prime mover when the input amountdetected by said third detection means is not smaller than a presetvalue.